It is well known to provide a passive seat belt system wherein one end of the belt is mounted inboard the seat and the outboard belt end is mounted on the door. A retractor is provided at one of the belt ends so that the belt is automatically wound and unwound between restraining and nonrestraining positions by the swinging movement of the door.
It is characteristic of such passive belt system that many layers of belt are wound upon the retractor reel when the door is closed and the belt assumes the restraining position. It has been observed in the prior art that the imposition of an occupant restraint load upon the belt subsequent to locking of the reel by a vehicle sensitive inertia locking mechanism causes the belt to tighten or spool-down on the reel and thereby extend the effective length of the restraint belt.
It is also known to employ a single reel mounted on the door for winding both the lap and shoulder belts. The simultaneous storage of both lap and shoulder belts on a single reel results in a relatively large diameter of belt wound upon the reel and accordingly increases the tendency for the belt to tighten or spool-down on the reel after the reel is locked by the onset of a sensed inertia condition.
The present invention provides a new and improved belt clamping mechanism in which the imposition of belt load on the reel subsequent to lockup of the reel against rotation induces shifting movement of the reel in the direction of belt pull to actuate a belt clamping mechanism.